Flexi Says: In the long history of life on earth, animals evolved to have bony skeletons about 550 million ago. There was more oxygen in the atmosphere than before and the chemistry of oceans also had changed. This lead to the evolution of animals that can incorporate the minerals in their surroundings into hard supportive structures called bones. Bones give a shape to our body and also provide mechanical strength. They allow for the attachment of muscles for coordinated movement and agility.